Gas turbine engines use an air compressor to provide a working fluid flow for combustion and power cycles. A portion of this working flow may be diverted into a cooling system to provide cooling air for turbine blades and vanes. Cooling air may be routed through a heat exchanger, then channeled through the interior of each blade and vane airfoil, and finally discharged from small holes in these airfoils into the turbine air stream to draw heat away from the surfaces of the airfoils. Cooling allows the use of high engine operating temperatures that would otherwise be detrimental to the structural integrity of the blades and vanes.
An unintended consequence of this removal and return of cooling air from the turbine system is that solid particle matter is entrained in the cooling air stream. Particles may become suspended in the cooling air by ingestion in the inlet air and by entrainment of corrosion from surfaces exposed to the air. Filters are used to remove larger particles from the cooling air flow.